Transistors and Applications Questions and Answers

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Q31
Which type of biasing is used for thermal stability in power amplifiers?
  • A Fixed bias
  • B Collector feedback
  • C Diode compensation
  • D Voltage divider
Answer: Option C
Explanation: Diode compensation and thermal feedback are used in power amplifiers for thermal stability.
Q32
In a class B amplifier, crossover distortion is caused by:
  • A Non-linear transistors
  • B Power supply ripple
  • C Both transistors off during zero crossing
  • D Temperature variations
Answer: Option C
Explanation: Crossover distortion occurs during the zero-crossing period when both transistors are off momentarily.
Q33
What is the typical efficiency of class A amplifier?
  • A 25%
  • B 50%
  • C 78.5%
  • D 90%
Answer: Option A
Explanation: Class A amplifiers have maximum theoretical efficiency of 25% for resistive loads and 50% for transformer-coupled.
Q34
Which transistor parameter is most temperature sensitive?
  • A Current gain (β)
  • B Base-emitter voltage
  • C Reverse saturation current
  • D Collector resistance
Answer: Option C
Explanation: Reverse saturation current (ICBO) doubles for every 10°C rise in temperature, making it highly temperature sensitive.
Q35
In a multistage amplifier, overall bandwidth is determined by:
  • A First stage
  • B Last stage
  • C Narrowest bandwidth stage
  • D Widest bandwidth stage
Answer: Option C
Explanation: The overall bandwidth is less than the bandwidth of individual stages due to cumulative effect of low and high frequency cutoffs.
Q36
What is the purpose of Miller compensation in op-amps?
  • A Increase bandwidth
  • B Improve stability
  • C Reduce power consumption
  • D Increase gain
Answer: Option B
Explanation: Miller compensation improves stability by introducing a dominant pole, though it reduces bandwidth.
Q37
Which type of feedback increases input impedance?
  • A Shunt feedback
  • B Series feedback
  • C Voltage feedback
  • D Current feedback
Answer: Option B
Explanation: Series feedback at input increases the input impedance of the amplifier.
Q38
In a transistor, the Early effect refers to:
  • A Temperature effect on β
  • B Base width modulation with VCB
  • C Early breakdown
  • D Storage time effect
Answer: Option B
Explanation: Early effect is the variation of base width with collector-base voltage due to base width modulation.
Q39
What is the typical value of transition capacitance in small signal transistors?
  • A 0.1-1 pF
  • B 1-10 pF
  • C 10-100 pF
  • D 100-1000 pF
Answer: Option B
Explanation: Transition capacitance in small signal transistors is typically in the range of 1-10 pF.
Q40
Which amplifier class has the highest efficiency?
  • A Class A
  • B Class B
  • C Class C
  • D Class D
Answer: Option D
Explanation: Class D amplifiers can achieve efficiencies up to 90-95% by using switching operation.

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